Cassini, Voyager missions suggest new picture of Sun’s interaction with galaxy

Posted: April 25, 2017 by oldbrew in research, solar system dynamics
Tags:

A compact model of the heliosphere, supported by the latest data [Credit: Dialynas, et al.]


It seems the interstellar magnetic field is a lot more powerful than scientists expected, as Phys.org reports.

New data from NASA’s Cassini mission, combined with measurements from the two Voyager spacecraft and NASA’s Interstellar Boundary Explorer, or IBEX, suggests that our sun and planets are surrounded by a giant, rounded system of magnetic field from the sun—calling into question the alternate view of the solar magnetic fields trailing behind the sun in the shape of a long comet tail.

The sun releases a constant outflow of magnetic solar material—called the solar wind—that fills the inner solar system, reaching far past the orbit of Neptune. This solar wind creates a bubble, some 23 billion miles across, called the heliosphere. Our entire solar system, including the heliosphere, moves through interstellar space.

The prevalent picture of the heliosphere was one of comet-shaped structure, with a rounded head and an extended tail.

But new data covering an entire 11-year solar activity cycle show that may not be the case: the heliosphere may be rounded on both ends, making its shape almost spherical. A paper on these results was published in Nature Astronomy on April 24, 2017.

“Instead of a prolonged, comet-like tail, this rough bubble-shape of the heliosphere is due to the strong interstellar magnetic field—much stronger than what was anticipated in the past—combined with the fact that the ratio between particle pressure and magnetic pressure inside the heliosheath is high,” said Kostas Dialynas, a space scientist at the Academy of Athens in Greece and lead author on the study.

An instrument on Cassini, which has been exploring the Saturn system over a decade, has given scientists crucial new clues about the shape of the heliosphere’s trailing end, often called the heliotail.

When charged particles from the inner solar system reach the boundary of the heliosphere, they sometimes undergo a series of charge exchanges with neutral gas atoms from the interstellar medium, dropping and regaining electrons as they travel through this vast boundary region. Some of these particles are pinged back in toward the inner solar system as fast-moving neutral atoms, which can be measured by Cassini.

Because these particles move at a small fraction of the speed of light, their journeys from the sun to the edge of the heliosphere and back again take years. So when the number of particles coming from the sun changes—usually as a result of its 11-year activity cycle—it takes years before that’s reflected in the amount of neutral atoms shooting back into the solar system.

Cassini’s new measurements of these neutral atoms revealed something unexpected—the particles coming from the tail of the heliosphere reflect the changes in the solar cycle almost exactly as fast as those coming from the nose of the heliosphere.

“If the heliosphere’s ‘tail’ is stretched out like a comet, we’d expect that the patterns of the solar cycle would show up much later in the measured neutral atoms,” said Krimigis.

Continued here.

Comments
  1. tallbloke says:

    “strong interstellar magnetic field—much stronger than what was anticipated in the past”

    Well fancy that.

    “the ratio between particle pressure and magnetic pressure”

    https://en.wikipedia.org/wiki/Magnetic_pressure

    Magnetic pressure is an energy density associated with a magnetic field. Any magnetic field has an associated magnetic pressure contained by the boundary conditions on the field. It is identical to any other physical pressure except that it is carried by the magnetic field rather than (in the case of a gas) by the kinetic energy of gas molecules. A gradient in field strength causes a force due to the magnetic pressure gradient called the magnetic pressure force.

    The magnetic pressure force is readily observed in an unsupported loop of wire. If an electric current passes through the loop, the wire serves as an electromagnet, such that the magnetic field strength inside the loop is much greater than the field strength just outside the loop. This gradient in field strength gives rise to a magnetic pressure force that tends to stretch the wire uniformly outward. If enough current travels through the wire, the loop of wire will form a circle.

  2. craigm350 says:

    Reblogged this on WeatherAction News and commented:
    Now that is interesting;
    Because these particles move at a small fraction of the speed of light, their journeys from the sun to the edge of the heliosphere and back again take years. So when the number of particles coming from the sun changes—usually as a result of its 11-year activity cycle—it takes years before that’s reflected in the amount of neutral atoms shooting back into the solar system.

    Cassini’s new measurements of these neutral atoms revealed something unexpected—the particles coming from the tail of the heliosphere reflect the changes in the solar cycle almost exactly as fast as those coming from the nose of the heliosphere.

  3. JB says:

    Someday the right hand will converse with the left, and astronomy will come up to speed with plasma research; the references to gas being spoken of for what it is.

  4. oldbrew says:

    ‘Relationship between electricity and magnetism

    In the early days scientists believed that electricity and magnetism are two separate forces. However, after the publication of James Clerk Maxwell, these forces are treated as interrelated forces.’

    http://www.physics-and-radio-electronics.com/physics/magnetism/relation-between-electricity-and-magnetism.html

  5. Gerry Pease says:

    The original phys.org article had comments supposedly from Hannes Alfven, who is known to have died in 1995.

    Hannes Alfvén – Wikipedia
    https://en.wikipedia.org/wiki/Hannes_Alfvén

    Hannes Olof Gösta Alfvén (Swedish: ; 30 May 1908 – 2 April 1995) was a Swedish electrical engineer, plasma physicist and winner of the 1970 Nobel Prize …

  6. oldbrew says:

    Another commenter suggests the person behind the H.A. mask is Wal Thornhill.

    http://www.holoscience.com/wp/

  7. TA says:

    How do magnetic fields operate over interstellar distances? It appears they do so, but how does a magnetic field remain coherent over these kinds of distances and separation in time?

  8. oldbrew says:

    Good question TA. The answer, if you can find one, probably depends on who you ask 😉

    This might be a clue – no guarantee of course…

    The cosmic microwave background (CMB) is the electromagnetic radiation left over from the time of recombination in Big Bang cosmology.
    http://en.wikipedia.org/wiki/Cosmic_microwave_background

  9. suricat says:

    Nice post oldbrew. I can’t think why the ‘heliosphere’ WOULD be ‘comet-shaped’. Though this becomes ‘murky waters’ for engineers like me (who, apparently, don’t understand ‘relativety’ too well).

    Any ‘particle’ at a temperature above ‘near absolute zero’ (the required ‘low KE’ (temperature) that displays ‘Boes-Einstein Condensate) displays properties of ‘electro-magnetic’ effect. Thus, the ‘CMB’ (Cosmic Microwave Background) temperature proves that at least, a weak ‘EM’ (ElectroMagnetic) field exists in ‘interstellar space’ (if not, we wouldn’t be able to ‘see’ the stars).

    tallbloke says: April 25, 2017 at 11:01 am

    “Well fancy that.”

    I assume this to be an acerbic remark Rog.

    ““the ratio between particle pressure and magnetic pressure””

    I don’t follow. Please expound. A ‘particle’ may well posess ‘zero electric quotient/potential’ 😦

    “Magnetic pressure is an energy density associated with a magnetic field. Any magnetic field has an associated magnetic pressure contained by the boundary conditions on the field.”

    You forgot to mention that the ‘only boundary’ for a ‘magnetic field’ is ‘another opposing magnetic field’

    Nuf said.

    Best regards, Ray.

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